Method for manufacturing photo-sintering particle, method for manufacturing photo-sintering target, and photo-sintering method

ABSTRACT

Provided is a method for manufacturing photonic sintering particles. According to an embodiment, the method includes: preparing nano particles; and forming oxide films having different thicknesses with reference to the thermal conductivity of a substrate, on which the nano particles are to be formed, on surfaces of the nano particles.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a method for manufacturing photonicsintering particles, a method for manufacturing a photonic sinteringtarget, and a photonic sintering method, and more particularly to amethod for manufacturing photonic sintering particles, a method formanufacturing a photonic sintering target, and a photonic sinteringmethod, which improve photonic sintering efficiency through control ofoxide films on surfaces of nano particles.

2. Description of the Prior Art

In recent years, as the electronic engineering technologies and theinformation technologies have developed, uses of portable electronicdevices have increased gradually. Currently, almost all of electronicproducts are manufactured through photolithographic processes. However,because a photolithographic process has 12 or more stages, causing theprocess complex, the process costs are high, manufacturing time is long,and the photolithographic process uses many toxic chemicals, it maycause environmental contaminations. Accordingly, studies on printingelectronics have been actively made to replace such a photolithographicprocess.

Printing electronics refer to electronic products in which patterns areformed through printing such as screen printing or gravure printing.This includes three stages of simple processes such as printing, drying,and sintering, and has advantages of low costs, anenvironmental-friendly aspect, a flexibility, a large-areamass-production, a low-temperature/simple process as compared with aconventional photolithographic process. Accordingly, the printingelectronics can be applied various electronic products such as flexibleelectronic products and solar cells.

The core technologies of printed electronic elements include sintering,and the electrical conductivity and the quality of the patterns aftersintering may depend on the sintering method and the sinteringcondition. The existing methods for sintering conductive ink currentlyincludes a thermal sintering method, but because sintering is performedat a temperature of 300° C., it cannot be applied to a flexiblesubstrate, and it requires a long process time and a chamber so it isnot suitable for mass-production.

Accordingly, laser sintering, plasma sintering, microwave sintering, andthe like have been suggested as a new sintering method, but they alsoare not suitable for mass-production, and the inventor(s) suggested awhite light ultra-shortwave photonic sintering method.

SUMMARY OF THE INVENTION

A technical problem to be solved by the present invention is to providea method for manufacturing photonic sintering particles, a method formanufacturing a photonic sintering target, and a photonic sinteringmethod having a high efficiency.

Another technical problem to be solved by the present invention is toprovide a method for manufacturing photonic sintering particles, amethod for manufacturing a photonic sintering target, and a photonicsintering method, by which photonic sintering can be achieved with ahigh dignity even in a silicon substrate.

Another technical problem to be solved by the present invention is toprovide a method for manufacturing photonic sintering particles, amethod for manufacturing a photonic sintering target, and a photonicsintering method having an excellent process convenience.

Another technical problem to be solved by the present invention is toprovide a method for manufacturing photonic sintering particles, amethod for manufacturing a photonic sintering target, and a photonicsintering method having an excellent competitiveness in price.

Another technical problem to be solved by the present invention is toprovide a method for manufacturing photonic sintering particles, amethod for manufacturing a photonic sintering target, and a photonicsintering method, by which mass-production can be easily achieved.

The objectives of the present invention are not limited to theabove-described ones.

According to an aspect of the present invention, a method formanufacturing photonic sintering particles may include: preparing nanoparticles; and forming oxide films having different thicknesses withreference to the thermal conductivity of a substrate, on which the nanoparticles are to be formed, on surfaces of the nano particles.

According to an embodiment, in the forming of the oxide films, oxidefilms of a first thickness may be formed on the surfaces of the nanoparticles when the thermal conductivity of the substrate is lower than apredetermined reference value, and oxide films of a second thickness maybe formed on the surfaces of the nano particles when the thermalconductivity of the substrate is higher than the predetermined referencevalue, and the first thickness may be smaller than the second thickness.

According to an embodiment, the predetermined reference value is 1 W/mK.

According to an embodiment, the first thickness may be 1% to 3% of thediameters of the nano particles, and the second thickness may be 3% to10% of the diameters of the nano particles.

According to another aspect of the present invention, a method formanufacturing a photonic sintering target may include 0: preparing nanoparticles; forming oxide films having different thicknesses withreference to the thermal conductivity of a substrate, on which the nanoparticles are to be formed, on surfaces of the nano particles; andmanufacturing a conductive target by providing a binder resin in thenano particles, on which the oxide films are formed.

According to an embodiment, in the forming of the oxide films, oxidefilms of a first thickness may be formed on the surfaces of the nanoparticles when the thermal conductivity of the substrate is lower than apredetermined reference value, and oxide films of a second thickness maybe formed on the surfaces of the nano particles when the thermalconductivity of the substrate is higher than the predetermined referencevalue, and the first thickness may be smaller than the second thickness.

According to an embodiment, the predetermined reference value may be 1W/mK.

According to an embodiment, the first thickness may be 1% to 3% of thediameters of the nano particles, and the second thickness may be 3% to10% of the diameters of the nano particles.

According to another aspect of the present invention, a photonicsintering method may include: forming oxide films having differentthicknesses with reference to the thermal conductivity of a substrate,on which the nano particles are to be formed, on surfaces of the nanoparticles; manufacturing a conductive target by providing a binder resinin the nano particles, on which the oxide films are formed; forming themanufactured conductive target on the substrate; and photonic-sinteringthe conductive target formed on the substrate.

According to an embodiment, in the forming of the oxide films, oxidefilms of a first thickness may be formed on the surfaces of the nanoparticles when the thermal conductivity of the substrate is lower than apredetermined reference value, and oxide films of a second thickness maybe formed on the surfaces of the nano particles when the thermalconductivity of the substrate is higher than the predetermined referencevalue, and the first thickness may be smaller than the second thickness,and in the photonic-sintering of the conductive target, light of a firstintensity may be irradiated to the substrate when the thermalconductivity of the substrate is lower than the predetermined referencevalue and light of a second intensity may be irradiated to the substratewhen the thermal conductivity of the substrate is higher than thepredetermined reference value, and the first intensity is lower than thesecond intensity.

According to another aspect of the present invention, a method formanufacturing photonic sintering particles may include determiningwhether it is necessary to form oxide films on the surfaces of the nanoparticles according to the characteristics of the substrate, on whichthe nano particles are to be formed; and when it is necessary to formthe oxide films on the surfaces of the nano particles, forming oxidefilms on the surfaces of the nano particles.

According to an embodiment, the characteristics of the substrate may bethermal conductivity, and when the thermal conductivity is 1 W/mK ormore, it may be determined that it is necessary to form oxide films onthe surfaces of the nano particles.

According to an embodiment, when the substrate includes silicon, it maybe determined that it is necessary to form oxide films on the surfacesof the nano particles.

According to another aspect of the present invention, a method formanufacturing a photonic sintering target may include: determiningwhether it is necessary to form oxide films on the surfaces of the nanoparticles according to the characteristics of the substrate, on whichthe nano particles are to be formed; when it is necessary to form oxidefilms on the surfaces of the nano particles, forming oxide films on thesurfaces of the nano particles; and manufacturing a conductive target byproviding a binder resin in the nano particles, on which the oxide filmsare formed.

According to an embodiment, the characteristics of the substrate may bethermal conductivity, and when the thermal conductivity is 1 W/mK ormore, it may be determined that it is necessary to form oxide films onthe surfaces of the nano particles.

According to an embodiment, when the substrate includes silicon, it maybe determined that it is necessary to form oxide films on the surfacesof the nano particles.

According to another aspect of the present invention, a photonicsintering method including: determining whether it is necessary to formoxide films on the surfaces of the nano particles according to thecharacteristics of the substrate, on which the nano particles are to beformed; when it is necessary to form oxide films on the surfaces of thenano particles, forming oxide films on the surfaces of the nanoparticles; manufacturing a conductive target by providing a binder resinin the nano particles, on which the oxide films are formed; forming themanufactured conductive target on the substrate; and photonic-sinteringthe conductive target formed on the substrate.

A photonic sintering method according to an embodiment of the presentinvention may include a step of forming and controlling oxide films ofcopper nano particles such that the copper nano particles have optimumphotonic sintering characteristics according to the kind of a substrate,a step of manufacturing a conductive ink including a polymeric binderresin, a step of printing the conductive ink on the substrate and dryingthe substrate, and a step of photonic-sintering the printed pattern byusing while light irradiated from a xenon flash lamp.

According to an embodiment of the present invention, oxide films can bereduced and sintered in a very short time of within several milliseconds(1 ms to 1000 ms) in a room temperature/atmospheric condition, andelectronic elements having high electrical conductivity and reliabilitycan be easily mass-produced.

In particular, according to an embodiment of the present invention,because a photonic sintering process may be performed on a siliconsubstrate, on which it is conventionally difficult to perform a photonicsintering process can become possible, the kinds of the substratesapplied can be expanded.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the presentinvention will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a flowchart illustrating a photonic sintering method accordingto an embodiment of the present invention;

FIGS. 2A and 2B are views illustrating step S150 of the photonicsintering method according to the embodiment of the present invention;

FIG. 3 is a view illustrating a photonic sintering method according toanother embodiment of the present invention;

FIG. 4 is a graph depicting resistances according to the kinds ofsubstrates and the thicknesses of oxide films;

FIG. 5 illustrates high resolution-transmission electron microscope(HR-TEM) pictures for explaining oxide films formed according to thekinds of the substrates;

FIG. 6 illustrates graphs depicting a change in X-ray diffraction (XRD)before and after sintering according to the thickness of an oxide filmof a conductive target formed in a polyimide (PI) substrate;

FIG. 7 illustrates graphs depicting a change in XRD before and aftersintering according to the thickness of an oxide film of a conductivetarget formed in a silicon substrate;

FIG. 8 illustrates an SEM picture according the thickness of an oxidefilm of a conductive target formed on a PI substrate; and

FIG. 9 illustrates an SEM picture according the thickness of an oxidefilm of a conductive target formed on a silicon substrate.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.However, the technical spirit of the present invention is not limited tothe embodiments, but may be realized in different forms. The embodimentsintroduced here are provided to sufficiently deliver the spirit of thepresent invention to those skilled in the art so that the disclosedcontents may become thorough and complete.

When it is mentioned in the specification that one element is on anotherelement, it means that the first element may be directly formed on thesecond element or a third element may be interposed between the firstelement and the second element. Further, in the drawings, thethicknesses of the films and the areas are exaggerated for efficientdescription of the technical contents.

Further, in the various embodiments of the present invention, the termssuch as first, second, and third are used to describe various elements,but the elements are not limited to the terms. The terms are used onlyto distinguish one element from another element. Accordingly, an elementmentioned as a first element in one embodiment may be mentioned as asecond element in another embodiment. The embodiments illustrated hereinclude their complementary embodiments. Further, the term “and/or” inthe specification is used to include at least one of the elementsenumerated in the specification.

In the specification, the terms of a singular form may include pluralforms unless otherwise specified. Further, the terms “including” and“having” are used to designate that the features, the numbers, thesteps, the elements, or combination thereof described in thespecification are present, and may be understood that one or more otherfeatures, numbers, step, elements, or combinations thereof may be added.Further, in the specification, “connected to” is used to mean aplurality of elements are indirectly or directly connected to eachother.

Further, in the following description of the present invention, adetailed description of known functions and configurations incorporatedherein will be omitted when it may make the subject matter of thepresent invention unnecessarily unclear.

FIG. 1 is a flowchart illustrating a photonic sintering method accordingto an embodiment of the present invention. Referring to FIG. 1, a methodfor manufacturing photonic sintering particles and a method formanufacturing a photonic sintering target will be described together.FIG. 2 is a view illustrating step S150 of the photonic sintering methodaccording to the embodiment of the present invention.

Referring to FIG. 1, a photonic sintering method according to anembodiment of the present invention may includes a step of providingnano particles (S110), a step of forming oxide films having differentthicknesses with reference to the thermal conductivity of a substrate,on which the nano particles are to be formed, on surfaces of the nanoparticles (S120), a step of manufacturing a conductive target byproviding a binder resin in the nano particles, on which the oxide filmsare formed (S130), a step of forming the manufactured conductive targeton the substrate (S140), and photonic-sintering the conductive targetformed on the substrate. Hereinafter, the steps will be described.

Step S110

In step S110, nano particles may be provided. The nano particles mayinclude at least one material, among gold, silver, and copper.Hereinafter, it is assumed that the nano particles are copper nanoparticles unless mentioned particularly.

Step S120

In step S120, oxide films having different thicknesses with reference tothe thermal conductivity of a substrate, on which the nano particles areto be formed, may be formed on surfaces of the nano particles,

The substrate, for example, may be a soft substrate or a rigidsubstrate. For example, the substrate may be formed of at least materialamong photo paper, PET, paper, polybutylene terephtalate, polyethyleneterephthalate, polysulfone, polyether, polyether imide, Poly(ethylenenaphthalate) (PEN), an acryl resin, heat-resistant epoxy, a BTepoxy/glass fiber, polyvinyl acetate (EVA), butyl rubber, polyarylate,and polyimide. Further, the substrate may be formed of at least onematerial, among glass, amorphous silicon, mono-crystaline silicon,poly-crystaline silicon, and ceramics.

Then, the thicknesses of the oxide films, which are to be formed on thesurfaces of the prepared nano particles, may be controlled according tothe characteristics of the substrate, for example, thermal conductivityand flexibility. For example, the substrate may have thermalconductivity and flexibility characteristics as described in Table 1according to the kind of the substrate.

TABLE 1 Category Flexible Non-flexible Kind of substrate AmorphousCrystalline I ET aper EN BT VA silicon silicon Thermal .52 .24 .05 .15.24 .34 1.8 149 conduc- tivity [W/mk]

According to an embodiment, oxide films of a first thickness may beformed on the surfaces of the nano particles when the conductivity islower than the predetermined reference, and oxide films of a secondthickness that is larger than the first thickness may be formed when thethermal conductivity is higher than the predetermined reference. In moredetail, the oxide films of a thickness of 1% to 3% of the diameters ofthe nano particles may be formed on the surfaces of the nano particleswhen the thermal conductivity of the substrate is lower than 1 W/mK, andthe oxide films of a thickness of 3% to 10% of the diameters of the nanoparticles may be formed on the surfaces of the nano particles when thethermal conductivity of the substrate is higher than 1 W/mK.

According to an embodiment, oxide films may be formed on the surfaces ofthe nano particles in various methods. For example, a method ofoxidizing nano particles by heating the nano particles in air with achamber, a hot plate, or the like may be used and also a method ofoxidizing nano particles through a plasma treatment and a separatepost-treatment immediately after the manufacturing of the nanoparticles, but the present invention is not limited thereto. Further,the thicknesses of the oxide films may be controlled by adjusting one ora combination of two or more of heating temperature, oxidation time, andoxygen partial pressure.

Through steps S110 and S120, photonic sintering particles according toan embodiment of the present invention may be manufactured. Hereinafter,step S130 will be described.

Step S130

In step S130, a conductive target may be manufactured by providing abinder resin to the nano particles on which the oxide films are formed.Then, the conductive target means a photonic sintering target, and maybe understood as a concept including a photonic sintering ink and apaste.

The binder resin may be added to improve the dispersion and reduction ofthe manufactured photonic sintering ink. The binder resin may include atleast material, among polyvinyl pyrrolidone (PVP), polyvinyl alcohol(PVA), polyvinyl butyral, polyethylene glycol, polymethyl methacrylate,dextran, azobis, and sodium dodecylbenzene sulfate. Then, the fractionof the binder may be 1 wt % to 50 wt %. Further, because the dispersionor reduction effect decreases if the weight average molecular weight ofthe binder is too low and the binder forms a agglomerate when it exceeds500,000, it is preferable that the weight average molecular weight of10,000 to 500,000 is used. The kind and the dosage of the binder mayvary according to the thickness of the oxide films of the copper nanoparticles.

A photonic sintering target may be formed by performing step S130 on thephotonic sintering particles manufactured through steps S110 and S120.Hereinafter, step S140 will be described.

Step S140

In step S140, the manufactured photonic sintering target may be formedon the substrate.

The photonic sintering target may be formed on the substrate in variousmethods. For example, at least one method, among screen printing, inkjetprinting, micro-contact printing, imprinting, gravure printing,gravure-offset printing, flexography printing, and spin coating, may beused.

Further, the photonic sintering target formed on the substrate may bedried in a drying process. For example, the photonic sintering targetformed on the substrate may be dried by a hot air blower, a heatingchamber, a hot plate, an infrared ray, or a combination thereof. Thedrying temperature may be set such that the substrate is not damaged. Ifthe substrate is a polymer substrate, the drying temperature may be in arange of 60° C. to 150° C.

Step S150

In step S150, the photonic sintering target formed on the substrate maybe photonic-sintered. The photonic sintering target is photonic-sinteredto become conductive while receiving light energy from ultra-shortwavewhite light emitted from a xenon lamp. In the photonic sinteringprocess, all the oxide films are reduced and sintered only whensufficient light energy is irradiated, and it is necessary to preventthe substrate from being damaged when high energy is instantaneouslyirradiated. Accordingly, the white light may be irradiated through amulti-stage photonic sintering technique for gradually reducing oxidefilms to increase the sintering effect.

Referring to FIG. 2A for helping understanding, in a state in which thephotonic sintering target 20 is formed on one surface of the substrate10, light 50 may be provided to the photonic sintering target 20 througha xenon flash lamp 30. Then, in order to improve optical efficiency, areflector 40 that reflects light to an object may be provided on oneside of the xenon flash lamp 30.

Then, the light provided to the photonic sintering target may becombined by various factors. For example, as illustrated in FIG. 2B, thefactors, such as light provision time, the intensity of light, and thepulses of light may be controlled. For example, the condition of theprovided light varies according to changes in the width of the pulses(0.01 ms to 50 ms), the gap of the pulses (0.01 ms to 100 ms), thenumber of the pulses (one to 100 times), the intensity of light (0.1J/cm² to 100 J/cm²), and accordingly, a total light energy may havelight energy of a maximum of 100 J/cm².

Then, the energy range for sintering may vary according to thesubstrate. For example, light of a first intensity may be irradiated tothe substrate when the thermal conductivity of the substrate is lowerthan a predetermined reference value, and light of a second intensitythat is stronger than the first intensity may be irradiated to thesubstrate when the thermal conductivity of the substrate is height thana 7 predetermined reference value. In more detail, the intensity oflight may be in a range of 0.1 J/cm² to 20 J/cm² when the thermalconductivity of the substrate is lower than 1 W/mK, and the intensity oflight may be in a range of 20 J/cm² to 100 J/cm² when the thermalconductivity of the substrate is higher than 1 W/mK.

Until now, the method for manufacturing photonic sintering particles,the method for manufacturing a photonic sintering target, and a photonicsintering method according to the embodiments of the present inventionhave been described with reference to FIGS. 1 and 2. Hereinafter, amechanism of an embodiment of the present invention will be described.

Photonic Sintering Mechanism Considering Characteristics of Substrate

A mechanism of a rapid photonic sintering process that usesultra-shortwave white light is a mechanism which, if light energy ofwhite light pulses irradiated from a xenon lamp reaches a target,converts the light energy into thermal energy to instantaneouslyincrease the temperature of a target layer so that the target layer issintered in a very short time. Accordingly, because not only the lightabsorption, the heat capacity, and the thermal conductivity of thetarget layer but also the photonic sintering characteristics of thetarget layer vary according to the physical property of the substrate,it is necessary to control the light irradiation condition and the nonoparticles according to the sintering atmosphere due to the variations.However, because conventionally the physical property of the substratehas not been recognized as a photonic sintering parameter, it isdifficult to enhance the photonic sintering efficiency. In particular,it has been a difficulty in studying a photonic sintering measure, thetarget of which is a substrate of a high thermal conductivity.

The inventor(s) suggested a technical solution that considers thecharacteristics of a substrate.

In order to reduce and sinter a photonic sintering target, thetemperatures of the photonic sintering target and/or the nano particleshave to reach a specific temperature level. Because thermal energy isconducted from the photonic sintering target to the substrate morerapidly as the thermal conductivity of the substrate becomes higher inan aspect of heat transfer, the light energy that has to be irradiatedto sinter the photonic sintering target increases. Accordingly, a lightirradiation condition for higher energy is necessary when a material ofa high thermal conductivity, such as silicon, is used than when asubstrate of a low thermal conductivity, such as a polymer, is used.

Accordingly, because the photonic sintering target is deprived ofthermal energy that is necessary for sintering by the substrate in thecase of the silicon substrate of a high thermal conductivity, photonicsintering characteristics can be enhanced when the thickness of theoxide films are thick.

Further, in thick oxide films, light irradiation energy for sinteringincreases as the thermal conductivity of the substrate increases, andthen, the photonic sintering target can be prevented from being burnedor being delaminated from the substrate.

Unlike this, in the case of a polymer (PI, PE, or the like) substrate ofa low thermal conductivity, because light energy for sintering has to beminimized to minimize damage to the substrate, and thus the photonicsintering characteristics can be enhanced when the thicknesses of theoxide films of nano particles are small.

Accordingly, according to an embodiment of the present invention,because thin oxide films and sintering light of a low intensity areprovided when the thermal conductivity of the substrate is low and thickoxide films and sintering light of a high intensity are provided whenthe thermal conductivity of the substrate is high, the conductivitycharacteristics of the photonic sintering target can be enhanced and thestability of the substrate can be achieved.

FIG. 3 is a view illustrating a photonic sintering method according toanother embodiment of the present invention. Referring to FIG. 3, amethod for manufacturing photonic sintering particles and a method formanufacturing a photonic sintering target will be described together.

Referring to FIG. 3, a step of providing nano particles (S210), a stepof determining whether it is necessary to form oxide films on thesurfaces of the nano particles according to the characteristics of thesubstrate, on which the nano particles are to be formed (S220), a stepof, when it is necessary to form oxide films on the surfaces of the nanoparticles, forming oxide films on the surfaces of the nano particles(S230), a step of manufacturing a conductive target by providing abinder resin in the nano particles, on which the oxide films are formed(S240), and a step of forming the manufactured conductive target on thesubstrate (S250), and a step of photonic-sintering the conductive targetformed on the substrate (S260). Hereinafter, the steps will bedescribed. Then, the repeated parts of the steps described above withreference to FIG. 1 will be omitted.

Step S210 will be omitted because it corresponds to step S110.

In step S220, it may be determined whether it is necessary to form oxidefilms on surfaces of the nano particles according to the characteristicsof the substrate, on which nano particles are to be formed.

According to an embodiment, when the characteristics of the substrate,for example, the thermal conductivity of the substrate is higher than apredetermined reference, it may be determined that it is necessary toform oxide films on the surfaces of the nano particles. Then, thethermal conductivity according to the predetermined reference may be 1W/mK.

Unlike this, according to the kind of the substrate, for example, whenthe substrate includes silicon, it may be determined that it isnecessary to form oxide films on the surfaces of the nano particles.

In step S230, when it is determined in the determination of step S220that it is necessary to form oxide films, oxide films may be provided tothe surfaces of the nano particles.

Steps S240, S250, and S260 correspond to steps S130, S140, and S150, anda detailed description thereof will be omitted.

According to the embodiment described with reference to FIG. 3, whichhas been described above, photonic sintering that considers thecharacteristics of the substrate is possible by the step of determiningwhether it is necessary to form oxide films according to thecharacteristics of the substrate.

The effects of the consideration of the characteristics of the substrateare described already with reference to FIGS. 1 and 2, a descriptionthereof will be omitted. Hereinafter, the characteristics of theembodiments of the present invention will be described with reference toFIGS. 4 to 9.

FIG. 4 is a graph depicting resistances according to the kinds ofsubstrates and the thicknesses of oxide films. FIG. 5 illustrates highresolution-transmission electron microscope (HR-TEM) pictures forexplaining oxide films formed according to the kinds of the substrates.FIG. 6 illustrates graphs depicting a change in XRD before and aftersintering according to the thickness of an oxide film of a conductivetarget formed in a PI substrate. FIG. 7 illustrates graphs depicting achange in XRD before and after sintering according to the thickness ofan oxide film of a conductive target formed in a silicon substrate. FIG.8 illustrates an SEM picture according the thickness of an oxide film ofa conductive target formed on a PI substrate. FIG. 9 illustrates an SEMpicture according the thickness of an oxide film of a conductive targetformed on a silicon substrate.

For experiments, embodiments 1 to 6 were prepared.

Embodiment 1

Copper nano particles having an average diameter of 100 nm were mixed inan oven of a temperature of 200° C. and were oxidized for 1 minute. PVPof 0.9 g was mixed with a diethylene glycol butyl ether (DGBE) solutionof 4 g and was dispersed for 30 minutes by using a sonicator. Afterbeing added to the mixture solution, the oxidized copper particles of 12g were dispersed for 40 minutes by using a 3-roll mill to manufacture acopper paste. After being printed in the form of an electrode on asilicon substrate by using a screen printer, the manufactured copperpaste was dried for 15 minutes by using infrared rays of a temperatureof 100° C. to finish an electrode pattern. Ultra-shortwave white lightwas irradiated to the electrode pattern. Then, the number of pulses ofthe ultra-shortwave white light was 40, the width of the pulses was 1ms, the interval between the pulses was 20 ms, and the total irradiationenergy was 60 J/cm²).

Embodiment 2

Copper nano particles having an average diameter of 100 nm were mixed inan oven of a temperature of 200° C. and were oxidized for 4 minutes. PVPof 0.9 g was mixed with a diethylene glycol (DEG) solution of 4.5 g andwas dispersed for 30 minutes by using a sonicator. After being added tothe mixture solution, the oxidized copper particles of 11.4 g weredispersed for 45 minutes by using a 3-roll mill to manufacture a copperpaste. After being printed in the form of an electrode on a siliconsubstrate by using a screen printer, the manufactured copper paste wasdried for 15 minutes by using infrared rays of a temperature of 100° C.to finish an electrode pattern. Ultra-shortwave white light wasirradiated to the electrode pattern. Then, the number of pulses of theultra-shortwave white light was 30, the width of the pulses was 1 ms,the interval between the pulses was 30 ms, and the total irradiationenergy was 55 J/cm²).

Embodiment 3

Copper nano particles having an average diameter of 100 nm were mixed inan oven of a temperature of 200° C. and were oxidized for 7 minutes. PVPof 0.9 g was mixed with a diethylene glycol (DEG) solution of 4.5 g andwas dispersed for 30 minutes by using a sonicator. After being added tothe mixture solution, the oxidized copper particles of 11.4 g weredispersed for 50 minutes by using a 3-roll mill to manufacture a copperpaste. After being printed in the form of an electrode on a siliconsubstrate by using a screen printer, the manufactured copper paste wasdried for 15 minutes by using infrared rays of a temperature of 120° C.to finish an electrode pattern. Ultra-shortwave white light wasirradiated to the electrode pattern. Then, the number of pulses of theultra-shortwave white light was 25, the width of the pulses was 1.5 ms,the interval between the pulses was 25 ms, and the total irradiationenergy was 50 J/cm²).

Embodiment 4

Copper nano particles of an average diameter of 40 nm were dispersed for30 minutes by using a sonicator after PVP of 0.9 g was mixed with adiethylene glycol (DEG) solution of 4.5 g. After being added to themixture solution, the oxidized copper particles of 11.4 g were dispersedfor 45 minutes by using a 3-roll mill to manufacture a copper paste.After being printed in the form of an electrode on a polyimide (PI)substrate by using a screen printer, the manufactured copper paste wasdried for 20 minutes by using infrared rays of a temperature of 100° C.to finish an electrode pattern. Ultra-shortwave white light wasirradiated to the electrode pattern. The, the irradiation time was 10ms, the number of pulses was 1, and the pulse energy was 12. 5 J/cm².

Embodiment 5

Copper nano particles having an average diameter of 40 nm were mixed inan oven of a temperature of 100° C. and were oxidized for three hours.PVP of 0.9 g was mixed with a diethylene glycol (DEG) solution of 4.5 gand was dispersed for 30 minutes by using a sonicator. After being addedto the mixture solution, the oxidized copper particles of 11.4 g weredispersed for 50 minutes by using a 3-roll mill to manufacture a copperpaste. After being printed in the form of an electrode on a polyimide(PI) substrate by using a screen printer, the manufactured copper pastewas dried for 1 minute by using a hot plate of a temperature of 100° C.to finish an electrode pattern. Ultra-shortwave white light wasirradiated to the electrode pattern. The, the irradiation time was 10ms, the number of pulses was 1, and the pulse energy was 15 J/cm².

Embodiment 6

Copper nano particles having an average diameter of 40 nm were mixed inan oven of a temperature of 200° C. and were oxidized for two hours. PVPof 0.9 g was mixed with a diethylene glycol (DEG) solution of 4.5 g andwas dispersed for 30 minutes by using a sonicator. After being added tothe mixture solution, the oxidized copper particles of 11.4 g weredispersed for 50 minutes by using a 3-roll mill to manufacture a copperpaste. After being printed in the form of an electrode on a polyimide(PI) substrate by using a screen printer, the manufactured copper pastewas dried for one minute by using a hot plate of a temperature of 100°C. to finish an electrode pattern. Ultra-shortwave white light wasirradiated to the electrode pattern. The, the irradiation time was 20ms, the number of pulses was 1, and the pulse energy was 15 J/cm².

Referring to FIG. 4, resistances of the cases in which the surface oxidefilms of the copper nano particles had different thicknesses could beidentified according to whether the substrate is a PI substrate having alow thermal conductivity or a silicon substrate. As illustrated in FIG.4 and Table 2, it could be identified that the conductivity becomes moreexcellent as the thickness of the oxide films becomes smaller in thecase of a PI substrate having a low thermal conductivity. Unlike this,it could be identified that the conductivity is still excellent eventhough the thickness of the oxide films becomes larger in the case of asilicon substrate having a high thermal conductivity. In particular, itcould be identified that the conductivity can be remarkably improved byforming oxide films on the photonic sintering target in the case of asilicon substrate.

TABLE 2 Thickness of oxide films 0.8 nm 2.1 nm 3.6 nm PI resistivity17.339 μΩ · cm 45.818 μΩ · cm 74.213 μΩ · cm Thickness of oxide films2.7 nm 5.8 nm 7.1 nm Silicon 15.3 μΩ · cm 10.87 μΩ · cm 16.13 μΩ · cmresistivity

Unlike this, it could be identified that both the two substrates couldnot be sintered by using photonic sintering when no oxide film of thecopper particles was present (0 nm and 0.2 nm). This is because thecopper patterns were burned out while reacting with oxygen in air whenwhite light of strong pulses is irradiated in the case of the coppernano particles with no oxide film.

FIG. 5 is a picture illustrating that the oxide films of a predeterminedthickness were formed on the surfaces of the copper nano particles, andno amorphous material (oxide film layer) was observed before thetreatment process for forming oxide films, and it could be identifiedthat optimized oxide films of 0.8 nm were formed in the PI substrate andoptimized oxide films of 5.8 nm were formed in the silicon substrateafter the oxidation process.

Referring to FIG. 6, a photonic sintering target was formed in the PIsubstrate, and an XRD graph according to variation of the thickness ofthe oxide films could be identified. Oxidized copper film reductionreactions by the reactions with the polymer surface modifiers coated onthe outside of the copper nano particles were generated, andaccordingly, it could be identified that the oxidized copper of thecopper nano particles having oxide films of a thickness of 3.6 nm orless was reduced to pure copper and was sintered. Meanwhile, it wasshown that many oxide films were still left after the irradiation ofultra-shortwave white light if excessive oxide films were formed and acopper oxide (II) (CuO) is excessively formed (FIG. 8), and electricalresistance is high. Accordingly, proper control of oxide films isnecessarily necessary in enhancing photonic sintering characteristics ofcopper nano ink.

Referring to FIG. 7, a photonic sintering target was formed in thesilicon substrate, and an XRD graph according to variation of thethickness of the oxide films could be identified. As illustrated in FIG.7, it could be identified that sintering cannot be achieved by formingoxide films of a small thickness of 0.2 nm (natural oxidation), andsintering can be achieved when the thickness of the oxide films is 5.8nm and 7.1 nm. That is, it also could be identified experimentally thatthe oxide films had to be thick in the case of the substrate having ahigh thermal conductivity.

Referring to FIGS. 8 and 9, it could be identified that the conductivitycharacteristics became worse because the number of pores increases asthe thickness of the oxide films becomes larger in the case of the PIsubstrate, and there is not any big difference between the conductivitycharacteristics when the thicknesses of the oxide films are 2.7 nm to7.1 nm.

According to the above-described embodiments of the present invention,optimum photonic sintering characteristics could be provided to the nanoparticles having oxide films according to the kind of the substrate.Accordingly, a photonic sintering process, which has been extremelydifficult to realize conventionally, may be performed even to asubstrate of a high thermal conductivity. Further, the photonicsintering efficiency can be enhanced by controlling the thickness ofoxide films and a photonic sintering condition differently according tothe characteristics of the substrate.

Although the preferred embodiments of the present invention have beendescribed in detail until now, the scope of the present invention is notlimited to the embodiments and should be construed by the attachedclaims. Further, it should be understood that those skilled in the artto which the present invention pertains may variously correct and modifythe present invention without departing from the scope of the presentinvention.

What is claimed is:
 1. A method for manufacturing photonic sinteringparticles, the method comprising: preparing nano particles; and formingoxide films having different thicknesses with reference to the thermalconductivity of a substrate, on which the nano particles are to beformed, on surfaces of the nano particles.
 2. The method of claim 1,wherein in the forming of the oxide films, oxide films of a firstthickness are formed on the surfaces of the nano particles when thethermal conductivity of the substrate is lower than a predeterminedreference value, and oxide films of a second thickness are formed on thesurfaces of the nano particles when the thermal conductivity of thesubstrate is higher than the predetermined reference value, and whereinthe first thickness is smaller than the second thickness.
 3. The methodof claim 2, wherein the predetermined reference value is 1 W/mK.
 4. Themethod of claim 2, wherein the first thickness is 1% to 3% of thediameters of the nano particles, and the second thickness is 3% to 10%of the diameters of the nano particles.
 5. A method for manufacturing aphotonic sintering target, the method comprising: preparing nanoparticles; forming oxide films having different thicknesses withreference to the thermal conductivity of a substrate, on which the nanoparticles are to be formed, on surfaces of the nano particles; andmanufacturing a conductive target by providing a binder resin in thenano particles, on which the oxide films are formed.
 6. The method ofclaim 5, wherein in the forming of the oxide films, oxide films of afirst thickness are formed on the surfaces of the nano particles whenthe thermal conductivity of the substrate is lower than a predeterminedreference value, and oxide films of a second thickness are formed on thesurfaces of the nano particles when the thermal conductivity of thesubstrate is higher than the predetermined reference value, and whereinthe first thickness is smaller than the second thickness.
 7. The methodof claim 6, wherein the predetermined reference value is 1 W/mK.
 8. Themethod of claim 6, wherein the first thickness is 1% to 3% of thediameters of the nano particles, and the second thickness is 3% to 10%of the diameters of the nano particles.
 9. A photonic sintering method,comprising: forming oxide films having different thicknesses withreference to the thermal conductivity of a substrate, on which the nanoparticles are to be formed, on surfaces of the nano particles;manufacturing a conductive target by providing a binder resin in thenano particles, on which the oxide films are formed; forming themanufactured conductive target on the substrate; and photonic-sinteringthe conductive target formed on the substrate.
 10. The method of claim9, wherein in the forming of the oxide films, oxide films of a firstthickness are formed on the surfaces of the nano particles when thethermal conductivity of the substrate is lower than a predeterminedreference value, and oxide films of a second thickness are formed on thesurfaces of the nano particles when the thermal conductivity of thesubstrate is higher than the predetermined reference value, and thefirst thickness is smaller than the second thickness, and wherein in thephotonic-sintering of the conductive target, light of a first intensityis irradiated to the substrate when the thermal conductivity of thesubstrate is lower than the predetermined reference value and light of asecond intensity is irradiated to the substrate when the thermalconductivity of the substrate is higher than the predetermined referencevalue, and the first intensity is lower than the second intensity.
 11. Amethod for manufacturing photonic sintering particles, the methodcomprising: determining whether it is necessary to form oxide films onthe surfaces of the nano particles according to the characteristics ofthe substrate, on which the nano particles are to be formed; and when itis necessary to form the oxide films on the surfaces of the nanoparticles, forming oxide films on the surfaces of the nano particles.12. The method of claim 11, wherein the characteristics of the substrateare thermal conductivity, and when the thermal conductivity is 1 W/mK ormore, it is determined that it is necessary to form oxide films on thesurfaces of the nano particles.
 13. The method of claim 11, wherein whenthe substrate comprises silicon, it is determined that it is necessaryto form oxide films on the surfaces of the nano particles.
 14. A methodfor manufacturing a photonic sintering target, the method comprising:determining whether it is necessary to form oxide films on the surfacesof the nano particles according to the characteristics of the substrate,on which the nano particles are to be formed; when it is necessary toform oxide films on the surfaces of the nano particles, forming oxidefilms on the surfaces of the nano particles; and manufacturing aconductive target by providing a binder resin in the nano particles, onwhich the oxide films are formed.
 15. The method of claim 14, whereinthe characteristics of the substrate are thermal conductivity, and whenthe thermal conductivity is 1 W/mK or more, it is determined that it isnecessary to form oxide films on the surfaces of the nano particles. 16.The method of claim 14, wherein when the substrate comprises silicon, itis determined that it is necessary to form oxide films on the surfacesof the nano particles.
 17. A photonic sintering method, comprising:determining whether it is necessary to form oxide films on the surfacesof the nano particles according to the characteristics of the substrate,on which the nano particles are to be formed; when it is necessary toform oxide films on the surfaces of the nano particles, forming oxidefilms on the surfaces of the nano particles; manufacturing a conductivetarget by providing a binder resin in the nano particles, on which theoxide films are formed; forming the manufactured conductive target onthe substrate; and photonic-sintering the conductive target formed onthe substrate.